Last week when Kris presented the custom udev rules to rename your network interfaces, I was a little confused about the wierd naming (010-netinterfaces.rules) of the custom rules files. I assumed the number at the beginning was to cause the file to be processed in some order (like the Sys V initscripts), but I wasn't sure and I had no idea about the rest of the name. I investigated this a little further and found this page. This seems to be a really thorough explanation of writing udev rules. From what I read there this guy confirms that the numbering at the beginning of the file is for order of execution and he also says that "in general" you want all of your custom rules to execute before the system provided rules. He suggests 10-local.rules as a filename, but on my Debian system there is a 020-xxx.rules file, so I am putting mine in a 010-local.rules. If you keep all of your rules in the single file it also has the benefit of being easily backed up.